1. Field of Invention
This invention relates generally to communication systems and methods. More particularly, this invention relates to communication systems and methods for broadcasting signals over an optical network.
2. Description of Related Art
A Wavelength-Division Multiplexed (WDM) network is an optical network on which information is transmitted using a plurality of optical signals having different wavelengths. For example, the network comprises optical fibers carrying optical signals generated by a plurality of laser sources modulated by digital or analog signals. The modulation incorporates the information to be transmitted into the optical signals.
Employing WDM networks to improve both the capacity and flexibility of optical networks is an area of active research. Current WDM networks support point-to-point wavelength connections in which a network is comprised of an origination node and any number of potential destination nodes located throughout the network. Wavelengths can be added or dropped at each potential destination node or can bypass each node.
Current research on WDM networks has focused on carrying switched services. Therefore, optical signals are either dropped entirely at a potential destination node or wholly transported through the potential destination node to move throughout the network. To receive a broadcast optical signal having a specific wavelength, a potential destination node drops the entire optical power relating to this specific wavelength, and converts the optical signal to an electronic signal. Electronic equipment at the node (such as an internet-protocol router) then uses this electronic signal to convey the transmitted information to a device at the destination node for use at the destination mode. Additionally, the electronic equipment at the node uses the electronic signal to modulate an optical source to generate another optical signal having the specific wavelength and then forwards the new optical signal to other node(s) on the optical network.
Such a node is complex and expensive. Moreover, the transmission time of the broadcast optical signal through a node is longer than the transmission time of the other optical signals through the node. This additional delay will degrade the performance of some services. Because some network management functions, such as restoration, are time sensitive, this delay may prevent the broadcast optical signal from being used for network management.
Therefore, there is a need for a low-cost, fast optical device that can be located at potential destination nodes and used to relay broadcast optical signals on a WDM network.
Accordingly, the exemplary embodiments of the invention provide an optical device for a node connected to an optical channel within an optical network. The node receives optical signals, each received signal having a different wavelength on the optical channel. The optical device includes a wavelength-selective optical tap that selectively drops a first portion of the optical power of a received optical signal having a specific wavelength. The device also transmits the optical signal having the specific wavelength to a next node. The transmitted optical signal has a second portion of the originally received optical power at the specified wavelength. The optical device may be referred to as a wavelength-selective optical tap.
This and other features and advantages of the invention are described in or are apparent from the following detailed description of the exemplary embodiments.